HTML in 30 minutes

HTML stands for HyperText Markup Language.
Using this, one can specify traits of richly formatted documents for a modern-day browser like Chrome, IE, Firefox etc.
An HTML document can display bold, italic, underlined text in various fonts and sizes with images, videos and interactive elements seamlessly woven into it.

For example:

Text on the left side is a table of links.

The title of this page has much bigger font than the rest of the page.

Some text on this page is bold and some is underlined.

And yet other text is highlighted.

All the above are examples of text-formatting in HTML.

Note: HTML is not a programming language as it does not provide conditional execution, loops and variables to the programmer.
Nevertheless, it can be used with scripting languages like Javascript to provide all the features of a programming language.